Einstein's 'Biggest Blunder' Turns Out to Be Right

What Einstein called his worst mistake, scientists are now depending on to help explain the universe.

In 1917, Albert Einstein inserted a term called the cosmological constant into his theory of general relativity to force the equations to predict a stationary universe in keeping with physicists' thinking at the time. When it became clear that the universe wasn't actually static, but was expanding instead, Einstein abandoned the constant, calling it the '"biggest blunder" of his life.

But lately scientists have revived Einstein's cosmological constant (denoted by the Greek capital letter lambda) to explain a mysterious force called dark energy that seems to be counteracting gravity — causing the universe to expand at an accelerating pace.

A new study confirms that the cosmological constant is the best fit for dark energy, and offers the most precise and accurate estimate yet of its value, researchers said. The finding comes from a measurement of the universe's geometry that suggests our universe is flat, rather than spherical or curved....